1. Technical Field
The present invention relates to active light-curable ink compositions, and particularly to a light-curable ink composition that can form favorably cured images having high abrasion resistance. The invention also relates to an ink set, an ink jet printing apparatus and an ink jet recording method using the active light-curable ink composition.
2. Related Art
In the ink jet recording method, an ink composition is deposited on a print medium, such as a paper sheet, by ejecting droplets of the ink composition, thereby performing printing. The ink jet recording method can print high-resolution and high-quality images at high speed. In general, the ink composition used in the ink jet recording method is essentially composed of an aqueous solvent, and contains a coloring material and a wetting agent, such as glycerol, for preventing clogging.
If aqueous ink repellent paper or cloth or aqueous ink repellent metal or plastic is used as the print medium, more specifically, if an ink composition is printed on a print medium, such as a plate or film made of, for example, phenol, melamine, vinyl chloride, acrylic resin or polycarbonate, the ink composition is required to contain a component capable of stably fixing the color material to the print medium.
According to this requirement, for example, U.S. Pat. No. 5,623,001 discloses a light-curable ink jet ink containing a color material, a photo-curing agent (radically polymerizable compound), and a (photo-radical) polymerization initiator. It is believed that this ink does not spread into print media and can enhance the quality of printed images.
The polymerization initiator is required to sufficiently adsorb light having the wavelength of the light source from the viewpoint of enhancing the image quality. For example, Japanese Unexamined Patent Application Publication No. 2007-182535 discloses photo-curable cyan, magenta, yellow and black ink compositions containing the same polymerization initiator irrespective of the color materials.
However, it has been found that ink compositions containing the same polymerization initiator as the composition disclosed in the above patent document cannot form sufficiently cured images having high abrasion resistance, depending on the color in some cases when being cured by active light. The color materials absorb different lights having different wavelengths, and the curing may be affected by light absorption of some of the color materials. The curability and abrasion resistance are degraded particularly in yellow, magenta and cyan images.